Add SpreadsheetLoader support for sign-magnitude

The spreadsheet loader defaults to 2’s complement when
extracting signed integers. With this commit, the
representation can be specified between parenthesis
in the raw value column, i.e.: int(2c), int(si).
Just ‘int’ will still default to 2’s.

Bug: 2259
Merge pull request #25 from fqqb/bug2259

Add SpreadsheetLoader support for sign-magnitude
added an option to count the number of bytes in the output file (needed for ACES quota checking)
Merge pull request #26 from fqqb/small-stuff

Small stuff
Allow extending EventViewer with extra columns

The current implementation needs to be configured
in the event-viewer.yaml file.
EventViewer: Make colors of warnings/errors easier on the eyes
Prevent NPE when no extra evt cols defined
Save column order of EventViewer in UI prefs

Save the column of an order with respect to the other columns in
the user preferences when the user closes the window.

When something in the configuration has changed (e.g. extra columns
are no longer present), it will do its best to restore the default
Event Viewer look.

This commit also brings a couple of changes to borders and colors
that appeared while testing the Event Viewer on Mac.
Merge pull request #27 from fqqb/evt-viewer

Extra columns in EventViewer
cleanup
cleanup and improved debugging
added the name to the constructor to be able to use it in system variables
make the index iterable
cleanup
log exceptions
cleanup
added configuration for dass retrieval time
 added system variables
 removed direct reference to DerivedValuesManager by splitting the consumers in ParameterRequestManager in two categories
added realtime parameter client
require lsb